Converting User app to System app.

Hi guys!

I need your help!

I wanna convert my app FakeGPS (paid version) to an system app.
I tried using apps like system app mover, and ES File Explorer, Link2SD, ect. (yes my phone is rooted)
but every time I try to convert the app and restart my phone the app is disappeared, and I have tried couple of times.

Sorry for the English it's not my home language.

Thanks in advance!